A fixing apparatus is provided in an image forming apparatus such as a photocopying machine and a printer, in which a toner image formed on a recording sheet is fixed on a recording sheet so as to obtain an image-formed medium. Moreover, in fixing apparatuses disclosed in Japanese Publication of Unexamined Patent Application, Tokukaihei, No. 8-137317 (published on May 31, 1996), U.S. Pat. No. 6,266,509 (corresponding to Japanese Publication of Unexamined Patent Application, Tokukai, No. 2000-29344 (published on Jan. 28, 2000)), and U.S. Pat. No. 6,463,249 (corresponding to Japanese Publication of Unexamined Patent Application, Tokukai, No. 2001-265151 (published on Sep. 28, 2001)), as releaser, oil such as a silicone oil is applied onto a fixing roller and a pressing roller so as to prevent (i) offset toner due to adhesion of the toner on a surface of the fixing roller, and (ii) twining a recording sheet, in order to attain stable image formation.
Referring to FIG. 8, described below is such a fixing apparatus in which oil is applied onto the fixing roller and the pressing roller. As shown in FIG. 8, a fixing apparatus 140 is provided with a fixing roller 101 and a pressing roller 102. Around the fixing roller 101, an upper sheet removing section 111, an upper cleaning roller 109, a fixing roller temperature detector 105, and an oil applying roller 107. Around the pressing roller 102, a lower sheet removing section 112, a lower clearing roller 110, and a pressing roller temperature detector 106 are provided. Moreover, the fixing roller 101 is provided with a fixing roller heater 103, while the pressing roller 102 is provided with a pressing roller heater 104.
Next, a system for applying the oil (releaser) in the fixing apparatus is explained below, referring to FIG. 8. Under the fixing apparatus 140, an oil tank 120 is provided. The oil for application is stored in the oil tank 120 always. Further, the oil tank 120 is provided with an oil remaining amount detecting sensor (for detecting how much oil is currently stored in the oil tank 120). When the oil is not enough, the oil remaining amount detecting sensor 127 gives warning on an operation panel of a main body apparatus and the like so as to urge to refill the oil. The oil is refilled via an oil supplying inlet 134.
The oil stored in the oil tank 120 is transferred to an oil dripping section 122 through an oil tube 126 by means of an oil pump 121.
The oil dripping section 122 has a tube-like (pipe-like) shape having a plurality of holes facing upward. The oil flows out through the plurality of holes and is dripped down, so as to be supplied to an oil applying member 123, which is provided under the oil dripping section 122.
When the oil is dripped on the oil applying member 123, the oil is absorbed into the oil applying member 123, which is made of such a material as to allow the oil to be spread therethrough, for example, felt. The oil applying member 123 touches the oil applying roller 107 so as to apply the oil onto the oil applying roller 107. The oil applying roller 107 is a roller (an intervening applying roller) located between the oil applying member 123 and the fixing roller 101. Further, the oil applied on the oil applying roller 107 is evenly spread out on the oil applying roller 107 by the applying blade 124. Then, the oil applying roller 107, on which the oil is spread out evenly, applies the oil on the fixing roller 101. Next, the fixing roller 101, on which the oil is applied, applies the oil on the pressing roller 102.
Moreover, excess oil, which remains unused in the oil application, is recollected by an oil pan 125 located under the oil applying member 123. The oil recollected in the oil pan 125 is returned to the oil tank 120 via a recollecting tube 128, which is connected to the oil pan 125.
Next, referring to FIG. 9, how the oil is applied from the oil applying member 123 to the oil applying roller 107 is explained in detail. The oil dripping section 122 drips oil 133 so as to supply the oil 133 to the oil applying member 123. The oil applying member 123 made of a material such as felt absorbs the oil 133 when the oil 133 is supplied to the oil applying member 123. Then, the oil 133 evenly diffuses through the oil applying member 123. The oil applying member 123 in which the oil 133 is evenly diffused, touches the oil applying roller 107 so as to apply to the oil applying roller 107 the oil 133 in the oil applying member 123.
Moreover, as shown in FIG. 9, the oil 133 is dripped on a supporting member 131 so that the oil 133 is dripped on a position (drip position) at a level higher or equal to a position (touch position) at which the oil applying member 123 touches the oil applying roller 107, and is supplied to the oil applying member 123 so as to be supplied to the oil applying roller 107 via the oil applying member 123. By having such a positional relationship, the oil 133 is transferred from the drip position at which the oil 133 is dripped on, to the touch position at which the oil applying member 123 touches the oil applying roller 107. As indicated by Arrow B in FIG. 9, the oil 133 flows down on a surface of the supporting member 131 from the drip position of the oil 133 to the oil applying member 123, and is absorbed into the oil applying member 123 and then passes through the oil applying member 123. Then, as indicated by Arrow B′, the oil 133 moves to the touch position at which the oil applying member 123 touches the oil applying roller 107, and is exuded out of the oil applying member 123 so as to be applied on the oil applying roller 107. Note that excess oil 133′, which remains unused in the oil application, is dropped down into the oil pan 125 so as to be recollected.
However, as shown in FIG. 10 in the system for applying the oil in the conventional fixing apparatus, as a result of long use of an image forming apparatus, toner and/or debris, which is adhered on the oil applying roller 107, is transferred onto the oil applying member 123 and accumulated thereon. Thus, as shown in FIG. 10, the toner and/or debris is adhered on a surface of the oil applying member 123, especially, the touch position at which the oil applying member 123 touches the oil applying roller 107. Moreover, the toner and/or debris adhered on the oil applying roller 107 comes from the fixing roller 101 and the pressing roller 102 at which the toner and/debris remains.
When the toner and/or debris is adhered on the touch position at which the oil applying member 123 touches the oil applying roller 107, the adhered toner and/or debris reduces an amount of the oil (the oil indicated by Arrow B′) exuded out of the oil applying member 123. As shown in FIG. 10, when the toner and/or debris is adhered on at the touch position, the adhered toner and/or debris hinders the movement of the oil 133 indicated by Arrow B′ and the exuding of the oil 133 from the oil applying member 123.
As described above, if the amount of the oil 133 to be exuded is reduced at the touch position due to the adhesion of the toner and/or debris, the dripping of the oil 133 in a constant amount simply leads to an increase in the amount of the excess oil 133′, while an amount of the oil to be applied on the oil applying roller 107 is reduced. Further, the reduction in the amount of the oil to be applied on the oil applying roller 107 decreases an amount of the oil to be applied on the fixing roller 101 and the pressing roller 102. This causes toner offset to the fixing roller 102, and jamming of a recording sheet, for example, due to twining of the recording sheet into the fixing roller 102 and the like.